J. van Prehn

Oversizing of Aortic Stent Grafts for Abdominal Aneurysm Repair: A Systematic Review of the Benefits and Risks

OBJECTIVE Sizing of aortic endografts is an essential step in successful endovascular treatment of aortic pathology, although consensus regarding the optimal sizing strategy is lacking. Some proximal oversizing is necessary to obtain a seal between the stent graft and the aortic wall and to prevent the graft from migrating, but excessive oversizing might influence the results negatively. In this systematic review, we investigated the current literature to obtain an overview of the risks and benefits of oversizing and to determine the optimal degree of oversizing of stent grafts used for endovascular abdominal aortic aneurysm repair. METHODS PUBMED, EMBASE and Cochrane Library databases were searched for articles related to the impact of proximal endograft oversizing on complications after endovascular aneurysm repair. After in- and exclusion, 23 relevant articles reporting on 8415 patients remained for analysis and critical appraisal. RESULTS Most studies that investigated neck dilatation are flawed by poor methodology. No clear relationship between proximal oversizing and neck dilatation relative to the first post-operative scan was found. None of the studies described a positive relationship between the degree of oversizing and the incidence of endoleaks. On the contrary, oversizing up to 25% seems to decrease the risk of proximal endoleaks. There are conflicting data regarding the risk of graft migration when oversizing by more than 30%. CONCLUSIONS Based on the best available evidence, the current standard of 10-20% oversizing regime appears to be relatively safe and preferable. Oversizing >30% might negatively impact the outcome after EVAR. Studies of higher quality are needed to further assess the relationship between proximal oversizing and the incidence of complications, particularly regarding the impact on aneurysm neck dilatation.

Dynamics of the aorta before and after endovascular aneurysm repair: a systematic review.

OBJECTIVE An overview of the knowledge of thoracic (TAA), and abdominal aortic aneurysm (AAA) dynamics, before and after endovascular repair, is given. METHODS Medline, EMBASE and the Cochrane database were searched for relevant articles. After inclusion and exclusion, 25 relevant articles reporting on aneurysm dynamics remained, allowing for comparison. Results provided in the included studies were assumed (statistically) significant if they were larger than the repeatability of the used method. RESULTS The sample size of dynamic studies is limited and translational studies are missing. Magnetic resonance angiography (MRA) and computed tomographic angiography (CTA) were shown to have lower inter-observer variabilities than ultrasonography (US). The distension of several relevant stent-graft-landing zones during the cardiac cycle in both the abdominal and thoracic aorta are significant (mean diameter change of the AAA neck in the included studies ranged from 0.9 mm to 2.4 mm; mean area change of the thoracic aorta ranged from 4.8% to 12.7% at various levels). This distension remained preserved after stent-graft placement. Preoperatively, the renal arteries displace per heartbeat. Significant movement of the aorta in the anteroposterior (AP) and lateral direction, during the cardiac cycle, was observed. CONCLUSION The aorta exhibits a wide variety of morphologic changes throughout the cardiac cycle. CTA and MRA are reliable modalities to investigate aortic shape changes during the cardiac cycle. Significant changes per heartbeat are reported in the AAA neck and thoracic aorta. The renal artery displaces per heartbeat. The clinical relevance of dynamic imaging has not been proven yet, but dynamic changes of the aorta have to be taken into account in stent-graft selection and future stent-graft design.

Aortic Compliance following EVAR and the Influence of Different Endografts: Determination Using Dynamic MRA

Purpose: To utilize dynamic magnetic resonance angiography (MRA) to characterize aortic stiffness (β) and elastic modulus (Ep) as indexes of wall compliance during the cardiac cycle and determine any influence of different endograft designs or the presence of endoleaks on these indexes. Methods: Eleven consecutive patients (11 men; median age 74 years, range 63–78) with abdominal aortic aneurysm (AAA) selected for endovascular repair were scanned pre- and postoperatively. Aortic area and diameter changes during the cardiac cycle were determined using dynamic MRA at 4 levels: 3 cm above the renal arteries, between the renal arteries, 1 cm below the renal arteries, and at the level of maximum aneurysm sac diameter. Ep and β were calculated. Data are presented as median (range); p<0.05 was considered significant. Results: Preoperatively, Ep and β were significantly higher at the level of the aneurysm sac compared to all other levels (p<0.05). Following EVAR, stiffness increased at this level (p<0.05). After implantation, patients with an Excluder endograft demonstrated Ep and β measurements at the aneurysm neck that were 94% and 60% higher, respectively, compared to those with a Talent (p<0.05) endograft. The presence of an endoleak had no effect on Ep or β. Conclusion: This study introduces the feasibility of dynamic MRA imaging—based calculations of aortic elastic modulus and stiffness. AAA patients demonstrate increased Ep and β at the level of the aneurysm sac. EVAR results in increased aneurysm sac Ep and β. Stent-graft design seems to alter Ep and β within the aneurysm neck, which may have consequences for endograft durability. The presence of an endoleak does not seem to have an effect on Ep or β.

Aortic Pulsatile Distention in Young Healthy Volunteers is Asymmetric : Analysis with ECG-gated MRI

OBJECTIVE Knowledge of aortic shape changes throughout the cardiac cycle can offer improved understanding of vascular pathophysiology and may have crucial impact on stentgraft design and EVAR durability. To understand underlying mechanisms of dynamic changes in aortic aneurysm (neck) morphology, the undiseased aorta has to be studied first. Objective is to visualize and characterize dynamic aortic shape changes in young healthy volunteers. MATERIALS AND METHODS Fifteen healthy volunteers (7 male, median age 24 year, range 18-28) were scanned using ECG-gated balanced gradient-echo MRI, with 16 reconstructed cardiac phases. Transverse scans were made perpendicular to the aorta: (A) above the aortic bifurcation, (B) infrarenal, (C) juxtarenal, (D) suprarenal and (E) above the celiac trunk. After aortic lumen segmentation, radial changes during the cardiac cycle were measured, from the center of mass, over 360 degrees, and plotted. An ellipse was fitted over the distention plots, yielding the direction (AP:0 degrees, Right: -90 degrees, Left: 90 degrees ) and magnitude of radius change over the major and minor axis. RESULTS Asymmetric distention was observed, with a variable rate per patient and level. Radius changes decreased from the proximal to distal aorta. Radius changes over the major axis ranged from 14% to 41%. At level A mean change in radius over the minor versus major axis was 1.4+/-0.2mm (17%) versus 1.6+/-0.2mm (20%), respectively. At B 1.7+/-0.4mm (22%) versus 2.0+/-0.4mm (25%), at C 1.7+/-0.4mm (22%) versus 2.2+/-0.4mm (27%) at D 2.0+/-0.4mm (25%) versus 2.4+/-0.5mm (30%) and at E 2.2+/-0.3mm (27%) versus 2.6+/-0.3mm (32%). Mean orientation of the major axis was (A) 0.8+/-23.3 degrees , (B) 1.8+/-31.3 degrees , (C) 14.0+/-15.5 degrees , (D) -28.8+/-48.0 degrees and (E) 18.4+/-22.2 degrees. CONCLUSIONS Aortic pulsatile distention in young healthy volunteers is asymmetric, with up to 41% radius change in the descending aorta. This study offers a frame of reference for dynamic imaging studies in patients with aortic pathology and provides a valuable non-invasive tool for future research into aortic distention, development and localization of vascular pathology.

The Influence of Different Types of Stent Grafts on Aneurysm Neck Dynamics after Endovascular Aneurysm Repair

OBJECTIVE Dynamic imaging provides insight into aortic shape changes throughout the cardiac cycle. These changes may be important for proximal aortic stent graft fixation, sealing and durability. The objective of this study is to analyse the influence of different types of stent grafts on dynamic changes of the aneurysm neck. METHODS Pre- and postoperative electrocardiography (ECG)-gated computed tomographic angiography (CTA) scans were obtained in 30 abdominal aortic aneurysm (AAA) patients, 10 each from three different types of stent grafts (10 Talent, Endurant, and Excluder). Each dynamic CTA dataset consisted of eight reconstructed images over the cardiac cycle. Aortic area and radius changes during the cardiac cycle were determined at two levels: (A) 3 cm above and (B) 1 cm below the lowermost renal artery. Radius changes were measured over 360 axes, and plotted in a polar plot. An ellipse was fitted over the plots to determine radius changes over the major and minor axis for assessment of the asymmetric aspect and most prominent direction of distension. RESULTS Baseline characteristics did not differ significantly between the three groups. Preoperatively, the aortic area increased significantly (p < 0.001) over the cardiac cycle in all patients at both levels: (A) mean increase 8.3 +/- 4.1% (2.0-17.3%); (B) mean increase 5.9 +/- 4.2% (1.9-12.4%). The postoperative aortic area increase over the cardiac cycle did not differ significantly from preoperative increases: (A) mean increase 9.9 +/- 2.2% (4.4-20.0%); (B) mean increase 7.7 +/- 2.4% (3.8-12.4%). The difference between radius change over the major and minor axis was significant both pre- and postoperatively for all three stent grafts, indicating asymmetric distension. Suprarenal, the distension showed a tendency to right-anterior and infrarenal to left-anterior. The distension and direction of the aortic expansion was preserved after stent grafting. There were no differences between the three types of stent grafts regarding their impact on the aortic distension or direction of this distension. CONCLUSION The aorta expands significantly and asymmetrically throughout the cardiac cycle. After implantation of abdominal aortic stent grafts, the aortic distension and direction of distension remain equally preserved in all three groups. The three stent graft types studied seem to be able to adapt to the asymmetric dynamic aortic shape changes.

Images in cardiovascular medicine. Aneurysm rupture after stent grafting: value of dynamic imaging.

A 67-year-old man presented at the emergency department with abdominal pain. Six years earlier, he was treated with an endograft for an infrarenal aortic aneurysm. Five years postoperatively, he developed a proximal endoleak caused by graft migration that was treated with implantation of a second endograft. On presentation, ECG-gated computed tomographic angiography …A 67-year-old man presented at the emergency department with abdominal pain. Six years earlier, he was treated with an endograft for an infrarenal aortic aneurysm. Five years postoperatively, he developed a proximal endoleak caused by graft migration that was treated with implantation of a second endograft. On presentation, ECG-gated computed tomographic angiography …